Intraoperative dynamic trialing

ABSTRACT

A dynamic trialing method generally allows a surgeon to perform a preliminary bone resection on the distal femur according to a curved or planar resection profile. With the curved resection profile, the distal-posterior femoral condyles may act as a femoral trial component after the preliminary bone resection. This may eliminate the need for a separate femoral trial component, reducing the cost and complexity of surgery. With the planar resection profile, shims or skid-like inserts that correlate to the distal-posterior condyles of the final insert may be attached to the distal femur after the preliminary bone resection to facilitate intraoperative trialing. The method and related components may also provide the ability of a surgeon to perform iterative intraoperative kinematic analysis and gap balancing, providing the surgeon the ability to perform necessary ligament and/or other soft tissue releases and fine tune the final implant positions based on data acquired during the surgery.

FIELD OF THE INVENTION

The present invention relates to trialing apparatus and methods in jointreplacement procedures and in particular relates to intraoperativedynamic trialing using preliminary bone preparations determinedaccording to a preoperative plan that correlates to the position andorientation of preoperatively planned final resections or resurfacingsprior to implanting one or more joint prostheses.

BACKGROUND OF THE INVENTION

Knee joint replacement procedures generally include preparation andresurfacing of the femur, tibia and/or patella. Briefly, the surgicalprocedure may involve calculated bone resections of each bone with thegoal of replacing damaged articular cartilage, restoring the joint lineand returning the patient to a pain-free movement of the knee joint.

In order to ensure proper knee joint kinematics, trial components of thefemur, tibia and/or patella may be used intraoperatively. During thesurgery, each bone is resected and the trial components are placed oneach respective bone to allow the surgeon to trial the joint through afull range of motion. During trialing, the surgeon generally assessesthe joint line, range of motion and ligament tension. Trial componentsgenerally represent various thicknesses, widths, or profiles toreplicate the final implant prosthesis. The trialing process allows thesurgeon to ensure proper knee joint function prior to the implantationof the final prosthesis.

Current methods of trialing and resecting the femur and tibia may leavethe surgeon with little or no flexibility in modifying the final boneresections following trialing the implant components. For example, ifthe bones are resected according to a final plan, and during trialingthe surgeon finds non-optimal joint kinematics, it may not be possibleto make additional bone resections to optimize the kinematics. Rather,the surgeon may only be left with limited options, for exampleperforming ligament releases, to attempt to optimize joint kinematicswhile remaining “stuck” with the bones resected according to the finalplan. Further, the more components that are involved in trialingprocedures generally translates to higher cost, greater complexity, andincreased duration of the trialing procedure. There exists a need fornew apparatus and methods to simplify the trialing procedure and toallow a surgeon to perform intraoperative dynamic trialing such thatinformation gained during trialing may be applied to modify the finalplanned bone resections.

BRIEF SUMMARY OF THE INVENTION

A dynamic trialing method generally allows a surgeon to perform apreliminary bone resection on the distal femur according to a curvedresection profile, a planar resection profile, or a combination thereof.With the curved resection profile, the distal-posterior femoral condylesmay act as a femoral trial component after the preliminary boneresection. This may eliminate the need for a separate femoral trialcomponent, reducing the cost and complexity of surgery. With the planarresection profile, shims or skid-like trials that correlate to thedistal-posterior condyles of the final femoral implant may be attachedto the distal femur after the preliminary bone resection to facilitateintraoperative trialing. The method and related components may alsoprovide the ability of a surgeon to perform iterative, intraoperativekinematic analysis and gap balancing, providing the surgeon the abilityto perform necessary ligament and/or other soft tissue releases and finetune the final implant positions based on data acquired during thesurgery. For example, by performing dynamic intraoperative kinematicanalysis using trial components that articulate in a way thatcorresponds to the final implant design plan, a surgeon may be able todebride osteophytes, remove menisci, and clean out around the posteriorcapsule to assess the affect the soft-tissue envelope has on kneepositional alignment. This may all be done prior to making the finalimplant resections, which the surgeon may choose to modify based on theresults of the dynamic intraoperative trialing.

In one embodiment, a dynamic trialing method includes creating a bonemodel of a distal femur of a patient and determining a curved resectionprofile on the bone model offset from distal and posterior nonresectedarticular surfaces of the distal femur. The distal femur may be resectedby making a preliminary resection along the curved resection profilesuch that a first area of bone is removed from the distal femur. Theresected distal femur may be engaged to a tibial trial coupled to aresected proximal tibia. Intraoperative kinematic analysis may beperformed by at least articulating the proximal tibia with respect tothe distal femur.

The step of performing kinematic analysis may include performingintraoperative gap balancing. The dynamic trialing method may includemaking a subsequent resection of the distal femur such that a secondarea of bone is removed from the distal femur. The subsequent resectionmay include making planar bone resections corresponding to matingsurfaces on a femoral implant. The subsequent resection may be performedaccording to a final design plan. Alternatively the subsequent resectionmay be performed according to a modified final design plan, the modifiedfinal design plan being determined, at least in part, based upon resultsof the kinematic analysis.

In one embodiment, the tibial trial may include a first condylar portionconnected to a second condylar portion, the first and second condylarportions each having a groove corresponding to an articular dish of atibial implant plateau. The tibial trial may include a tibial trialinsert and a template, the tibial trial insert being removable from thetemplate. The dynamic trialing method may further include the step ofremoving the tibial trial insert from the template and inserting analternative modular tibial trial insert into the template.

In another embodiment, the tibial trial may include a first inserthaving a proximal surface and a distal surface and a second inserthaving a proximal surface. The proximal surface of the first insert mayhave two grooves corresponding to articular dishes of the tibial implantplateau. The first insert may have at least two pegs extending distallyfrom the distal surface of the first insert and the second insert mayhave at least two holes on the proximal surface of the second insert,the at least two pegs being configured to be inserted into the at leasttwo holes.

In a further embodiment, the tibial trial may include a tibial inserthaving a first condylar portion configured to mate with a first grooveinsert and a second condylar portion configured to mate with a secondgroove insert. The first and second groove inserts may each have anarticulation surface corresponding to the articular dish of the tibialimplant plateau.

In still a further embodiment, the dynamic trialing method may includethe step of coupling first and second femoral shims to first and secondcondyles of the distal femur after the step of resecting the distalfemur by making a preliminary resection. The first and second femoralshims may each have an articulation surface configured to match a shapeof the femoral implant. The first and second femoral shims may each havea bone contacting surface with a peg extending therefrom, the pegs beingconfigured to facilitate fixing the first and second femoral shims tothe resected distal femur.

In another embodiment, the tibial trial may include a first condylarportion, a second condylar portion and at least one insert surface, theat least one insert surface being connected to at least one expandablecomponent having a volume that may expand or contract and also beingconfigured to remain at a constant pressure. The tibial trial may haveexactly one insert surface and exactly one expandable component, thefirst and second condylar portions being connected to one another.Alternately, the tibial trial may have two insert surfaces and twoexpandable components, a first insert surface corresponding to a firstexpandable component and the first condylar portion, and a second insertsurface corresponding to a second expandable component and a secondcondylar portion. The tibial trial may include a connecting memberphysically connecting the first condylar portion to the second condylarportion, the first expandable portion being fluidly isolated from thesecond expandable portion. At least one expandable component may be abellows. At least one expandable component may be connected to a fluidsource configured to pump air and/or fluid, e.g. saline, into theexpandable component.

In another embodiment of the invention, a dynamic trialing method mayinclude the step of creating a bone model of a distal femur of a patientand determining a preliminary resection profile on the bone model. Themethod may also include resecting the distal femur by making apreliminary resection along the preliminary resection profile such thata first area of bone is removed from the distal femur. The preliminaryresection profile may be determined, at least in part, based on afeature of a final design plan of a femoral implant. The final designplan of the femoral implant may include a femoral implant flexion axis,and the preliminary resection profile may be based on the femoralimplant flexion axis. The preliminary resection profile may include aflexion axis, the flexion axis of the preliminary resection profilebeing coaxial with the femoral implant flexion axis. The method may alsoinclude the step of performing intraoperative kinematic analysis by atleast articulating the proximal tibia with respect to the distal femur,and may also include the step of performing intraoperative gapbalancing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of one embodiment of a non-resected distal femur.

FIG. 2. is a side view of the distal femur of FIG. 1 including a curvedline indicating a preliminary resection profile along with a pluralityof planar lines indicating a final projected cut plan, including a finalplanned femoral implant position superimposed on the distal femur.

FIGS. 3A-C are side, perspective, and front views of the distal femur ofFIG. 1 after a preliminary bone resection has been performed.

FIG. 3D is a front view of the distal femur of FIG. 1 after an alternatepreliminary bone resection has been performed.

FIG. 4A is a side view of one embodiment of a non-resected proximaltibia.

FIG. 4B-C are side and perspective views of the proximal tibia of FIG.4A after a preliminary bone resection has been performed according to apreliminary resection profile.

FIG. 4D is a side view of the proximal tibia of FIG. 4A after thepreliminary bone resection along with a line indicating the finalprojected cut plan, including a final planned tibial implant positionsuperimposed on the proximal tibia.

FIG. 5 is a perspective view of one embodiment of a monolithic tibialtrial.

FIGS. 6A-C are multiple views of one embodiment of a tibial implant.

FIGS. 7A-B are perspective views of a knee joint moving from extensionto flexion using the tibial trial of FIG. 5.

FIGS. 8A-B are perspective and side views of femoral shims.

FIG. 8C is a side view of one embodiment of a femoral implant.

FIG. 8D is a side view showing a relationship between a femoral implantand a femoral shim.

FIGS. 9A-B are perspective views of an alternate embodiment of femoralshims.

FIG. 9C is a perspective view of another embodiment of femoral shims.

FIG. 9D is a perspective view of a prepared femur corresponding to thefemoral shims of FIG. 9C.

FIG. 9E is a perspective view of a further embodiment of femoral shims.

FIG. 9F is a side view of a distal femur including broken linesindicating a preliminary planar resection profile along with a pluralityof solid planar lines indicating a final projected cut plan, including afinal planned femoral implant position superimposed on the distal femur.

FIG. 9G is a side view of the distal femur of FIG. 9F after apreliminary bone resection has been performed according to the planarresection profile.

FIGS. 9H-J are perspective and side views of alternate femoral shimsconfigured for use with the distal femur of FIG. 9G.

FIG. 9K is a perspective view of the distal femur of FIG. 9G illustratedwith respect to the position of femoral shims of FIGS. 9H-J.

FIG. 10 is a perspective view of a distal femur with femoral shimsattached thereto.

FIG. 11A is a perspective view of one embodiment of a tibial insert.

FIG. 11B is a perspective view of one embodiment of an expandable andcontractable tibial insert.

FIG. 11C is a perspective view of one embodiment of a modified surfaceof the tibial insert of FIG. 11B.

FIG. 11D is a top perspective view of an alternate embodiment ofexpandable and contractable medial and lateral tibial inserts.

FIG. 11E is a top perspective view of the tibial insert of FIG. 11D withoptional connecting hardware illustrated.

FIGS. 12A-B are perspective and front views of one embodiment of amodular tibial trial according to an aspect of the invention.

FIGS. 13A-B are perspective and front views of another embodiment of amodular tibial trial insert and template according to an aspect of theinvention.

FIGS. 14A-B are perspective and front views of another embodiment of amodular tibial trial insert and template according to another aspect ofthe invention.

FIGS. 14C-F are top views of the various sized templates housing theinsert of FIGS. 14A-B therein.

FIGS. 15A-B are perspective and side views of one embodiment of amonolithic tibial insert according to another aspect of the invention.

FIG. 15C is a top view of the monolithic tibial insert of FIGS. 15A-Boverlaid on a larger monolithic tibial insert.

FIGS. 16A-B illustrate perspective views of a dual-use tibial trialaccording to another aspect of the invention.

FIGS. 17A-B illustrate perspective views of another dual-use tibialtrial according to an aspect of the disclosure.

DETAILED DESCRIPTION

As used herein, the term “distal” means more distant from the heart andthe term “proximal” means closer to the heart. The term “inferior” meanstoward the feet and the term “superior” means towards the head. The term“anterior” means towards the front part of the body or the face and theterm “posterior” means towards the back of the body. The term “medial”means toward the midline of the body and the term “lateral” means awayfrom the midline of the body. Also, as used herein, the terms“resecting,” “resurfacing,” and “bone preparation” are intended to beinterchangeable and generally refer to removing or reshaping bone.

FIG. 1 illustrates a distal portion of a non-resected distal femur 100prior a knee replacement procedure. As illustrated, a first condyle 110includes a posterior portion 120, a distal portion 130, and an anteriorportion 140. Generally, in total knee arthroplasty (“TKA”) procedures,up to five cuts are made to the distal femur 100, including distal,posterior, anterior, posterior chamfer, and anterior chamfer cuts.Following one or more of these cuts, a femoral trial component may beutilized with other trial components, for example a tibial trialcomponent, to assess joint function prior to implanting a femoralprosthesis on the resected distal femur.

The distal femur 100 is illustrated in FIG. 2 after a preliminary bonepreparation is made, outlined by broken line 150, to the posteriorportion 120 and distal portion 130 of the distal femur 100. Thepreliminary bone preparation may take the form of a preliminary boneresection made along a preliminary resection profile 150. Althoughillustrated as substantially a curved resection profile, the preliminaryresection profile may take the form of a planar resection profile, or acombination of a curved and planar resection profile. This preliminarybone resection along a curved resection profile of the distal femur 100may be performed partly or fully by a robotic machining tool such as arotating burr. The particular curved resection profile may be determinedwith the aid of a computer and may be determined based on a finalimplant design plan, including a flexion axis, for example, of a femoralimplant 180 located in a desired position on distal femur 100. Thecomputer may first be used to create a bone model of portions of thedistal femur 100 to aid in the determination of the preliminaryresection profile 150 and other operative plans. The preliminaryresection profile 150 may be offset from distal and posteriornonresected articular surfaces of the distal femur 100, such as theposterior portion 120 of the distal femur. During the preliminary boneresection, a first area of the distal femur 100 is removed, representedby the difference between the articular surface 145 of non-resecteddistal femur 100 illustrated in FIG. 1 and the remaining portions up tothe preliminary resection profile 150 illustrated in FIG. 2. Thedistance between the profile of articular surface 145 and preliminaryresection profile 150 is approximately 4-5 mm along the length of eachprofile. Preferably, the preliminary resection profile 150 is plannedsuch that, after the preliminary bone resection is made according to thecurved resection profile, the curved surface of the prepared distalfemur is coaxial with the final planned position of the femoral implant180. That is, both share a common axis with the desired, preoperativelyplanned flexion axis 160, which is derived during preoperative planning.This provides a correlation between the final positional alignment ofthe femoral implant 180 and the resultant kinematics being assessedduring trial reduction. The correlation may be determined regardless ofwhether, for example, a mechanical-classical or an anatomical alignmentmethodology is selected during the preoperative planning process. Thismay also provide the ability for the distal femur 100 itself to act as atrial for the femoral implant 180, described in more detail below.

The distal femur 100 in FIG. 2 is also superimposed with a finalprojected cut plan 170 representing the final planned distal, anterior,posterior, anterior chamfer and posterior chamfer cuts in the distalfemur. As can be seen, the preliminary resection profile 150 may notinterfere with the final projected cut plan 170. As described above, thepreliminary bone resection removes between approximately 4 mm andapproximately 5 mm of bone stock. It may also be preferred that thedistance between the final projected cut plan 170 and the preliminaryresection profile 150 along the articulating portion of the distal femur100 is no more than between approximately 2 mm and approximately 3 mm.As is described in more detail below, this distance allows the surgeonto make small rotational and translational adjustments to the projectedfinal cut plan 170 such that the actual final cuts vary slightly fromthose originally planned to account for information learned duringtrialing. This provides the surgeon with the ability to determineintraoperatively that modifications to the final projected cut plan 170,which modifications may include rotational and/or translationaladjustments to the six degrees of freedom of the femoral implant 180,which are made to optimize joint kinematics, while still having enoughbone remaining to perform additional resections to implement themodified final plan.

In certain embodiments described herein, a femoral implant 180 with a“single radius” may be used with the methods described herein, althoughother implants, such as an implant with a j-curve design, may also beused. Studies of kinematics and biomechanics have indicated thatconstant femoral condylar radii in natural knee motion are centeredabout the transepicondylar axis. Centering the radius of curvature aboutthe transepicondylar axis provides ligament isometry, not only in fullextension and 90 degrees of flexion, but through the entire range ofmotion. The surgical plan described above takes into account a femoralimplant that is designed with a “single radius,” as is shown anddescribed, for example in U.S. Pat. No. 5,824,100, the disclosure ofwhich is hereby incorporated by reference herein in its entirety. Thesingle radius centered about the epicondylar axis reproduces naturalknee movements designed to minimize the quadriceps forces required forextension thereby maximizing muscle efficiency. However, as is describedbelow, benefits may still be obtained from performing intraoperativetrialing after performing a preliminary bone resection corresponding toan implant that is not designed with a “single radius.”

During preoperative planning, the distal femur 100 is additionallysuperimposed with a femoral implant 180 in phantom lines, the femoralimplant being illustrated in a final position after the final cuts havebeen made to the distal femur 100. In one example, the distance betweenthe flexion axis 160 and the outer surface of the femoral implant 180are approximately equal along the portions of the femoral implant thatarticulate. Having a constant center of rotation or a single radius forboth the distal femur 100 prepared according to the preliminaryresection profile 150 and the femoral implant 180 allows for the distalfemur itself to act as a trial for the femoral implant, eliminating theneed for separate femoral trials. However, even with an alternativefemoral implant that does not have a “single radius,” the final positionof the implant may be used to derive the proper planned position of thefemoral component, usually in a measured resection position (as opposedto a flexion axis) which may be used to create an alternativepreliminary resection profile. For example, an alternative preliminaryresection profile may include a number of planar cuts as part of aplanar resection profile, or a combination of planar and curved cuts.Apparatus discussed below may be attached to the distal femur after thepreliminary bone resection, and intraoperative trialing corresponds tofinal implant kinematics may be performed.

FIGS. 3A-B illustrate different views of the distal femur 100 after thepreliminary bone resection is made according to the preliminaryresection profile 150. FIG. 3A also illustrates the final projected cutplan 170 as a broken line. Using the illustrated plan, after thepreliminary bone resection, the femoral condyles 110, 115, each have arounded articulating surface 152 with a flexion axis that is coaxialwith the flexion axis of the femoral implant when positioned accordingto the preoperative plan. In this embodiment, a first end of the roundedarticulating surface 152 transitions into an anterior stop 154 and asecond end of the rounded articulating surface 152 transitions into aposterior stop 156. FIG. 3C illustrates a front view of the distal femur100 after the preliminary bone resection is made according to thepreliminary resection profile 150. As can be seen, the condyles 110, 115have a radius in the sagittal plan only, with the frontal plane of thecondyles being relatively planar. However, as illustrated in FIG. 3D, analternative preliminary bone resection according to an alternatepreliminary resection profile may include machining the condyles 110,115 so that they are curved in both the sagittal, coronal and transverseplanes. This additional curvature may better accommodate rotation of thefemur on the tibia during the dynamic trialing step.

A non-resected proximal tibia 200 is illustrated in FIG. 4A prior toperforming any bone preparation. Similar to the procedure describedabove for the distal femur 100, the proximal tibia 200 may bepreliminarily resected in a first step according to a preliminaryresection profile 250. The preliminary resection profile may beshallower than the final planned cut 270. The preliminary bone resectionis mostly or completely flat or planar, as best illustrated in FIG. 4C.FIG. 4D illustrates the proximal tibia 200 after the preliminary boneresection has been made according to the preliminary resection profile250. Superimposed on FIG. 4D are the final planned cut 270 and a tibialimplant 280 positioned on the proximal tibia 200 in a final position. Itshould be noted that a preliminary bone resection need not be performedon the proximal tibia 200 in all cases, and in some embodiments theproximal tibia may be finished completely according to a final plan inone step without first performing a preliminary bone resection thatallows for further adjustments.

FIG. 5 illustrates one embodiment of a tibial trial insert 300 fortrialing after the preliminary bone resection is performed according tothe preliminary resection profiles 150, 250 in the distal femur 100 andthe proximal tibia 200, respectively. The tibial trial insert 300 mayinclude a first groove or sulcus 310 and a second groove or sulcus 320.The grooves may take the form of dished plateaus that correlate with thearticular dishes of the tibial implant plateau. The first and secondgrooves 310, 320 may be sized and positioned to articulate with thearticulating surfaces 152 of the first and second condyles 110, 115after the preliminary bone resection has been performed on the distalfemur 100. In the particular embodiment illustrated, the tibial trialinsert 300 is monolithic. That is, the tibial trial insert 300 is formedfrom a single piece of material.

The particular position of the grooves 310, 320 of tibial trial insert300 may depend upon the particular tibial implant 280 intended for use.FIGS. 6A-C illustrate top, side, and bottom views of an exemplary tibialimplant 280, respectively, to be implanted onto the proximal tibia 200after the final tibial resection is performed (which is performed aftertrialing with a tibial trial insert 300). As best illustrated in FIG.6B, the distance d between the anterior portion of post 282 and theanterior portion of tibial implant 280 may be related to the position ofthe grooves 310, 320 of the tibial trial insert 300. For example, theanterior portions 311, 321 of the respective grooves 310, 320 wheninserted on the proximal tibia 200 during trial may align with theanterior portion of post 282 when the tibial implant 280 is implanted onthe proximal tibia 200. In other words, the grooves 310, 320 of thetibial trial insert 300 should be positioned with respect to thegeometry of the final tibial implant 280 such that articulation betweenthe distal femur 100 (after the preliminary bone resection) and thetibial trial insert throughout the range of motion corresponds to thearticulation between the femoral implant 180 and the tibial implantaccording to the final design plan.

After the preliminary resections of the distal femur 100 and proximaltibia 200 are performed, the surgeon may perform trialing. FIG. 7Aillustrates the distal femur 100 and proximal tibia 200 in extensionwith tibial trial insert 300 positioned on the proximal tibia. In thisposition, the rounded articulating portions 152 of each condyle 110, 115of the distal femur 100 sit within the respective grooves 320, 310 ofthe tibial trial insert 300. In extension, the anterior stops 154 makecontact with an anterior portion of the tibial trial insert 300, settingan approximate limit to how far the knee may be placed into extension.In flexion, as illustrated in FIG. 7B, the posterior stops 156 makecontact with a posterior portion of the tibial trial insert 300, settingan approximate limit to how far the knee may be placed into flexion.

The shape of the distal femur 100 following the preliminary boneresection is configured to correspond to the shape of the femoralimplant 280, for example by having coaxial flexion axes, and toarticulate with the tibial trial insert 300, as described above. Thismay provide the ability for the surgeon to take the knee through a rangeof motion to perform trialing without the need of a separate femoraltrialing component and, as described above, correlate to the positionalalignment of the final design plan of the implants. For example, theknee may be taken through a range of motion from extension, throughmid-range flexion and then into deep flexion (for example, inapproximately 0, 30, 60, 90 and 120 degrees of flexion) to analyze thekinematics of the joint. In each desired position, the surgeon maydetermine the size of the gap between each femoral condyle 110, 115 andthe proximal tibia 200 to determine whether the gaps are properlybalanced. By articulating the proximal tibia 200 with respect to thedistal femur 100, the surgeon may determine a second area of bone toremove from the distal femur 100. This second removal of bone may beeither a secondary machining for fine tuning, or may be an adjustment tothe final femoral cut plan 170.

The decision of whether any change should be made to the final designplan may be based on a number of positional alignment target values. Forexample, one particular target may be that the gaps in both flexion andextension result in no more than two degrees offset from the neutral,mechanical axis regarding the overall limb alignment, although othertarget values, including for example one degree or three degrees, may beused. Another goal may be that the flexion gap should be equal to orgreater by approximately 3 mm relative to the extension gap, althoughgreater or smaller targets may be used. A further target may be that theflexion gap produces a force measurement that is equal or up toapproximately 10% greater than the force measurement produced by theextension gap, although other target percentages may be appropriate. Theabove gap balancing targets are merely illustrative and other targetsmay be implemented as desired by the surgeon. If the values determinedduring this kinematic analysis are not acceptable, the surgeon mayrelease soft tissue to attempt to reach acceptable values. Alternativelyor in addition to soft tissue release, the surgeon may adjust therotational and/or translational degrees of freedom of the implantposition in the design model and/or perform additional bone removalbased on the new design model. After the surgeon performs fine tuningand/or minor adjustments, if necessary, he may repeat the kinematicanalysis to determine if the new values are acceptable. Either or bothof these steps may be repeated in an iterative fashion until the surgeonis satisfied with the kinematic analysis at this intermediate stage.

FIGS. 8A-B illustrate shims 400 that may be attached to the distal femur100 after the preliminary femoral bone resection is performed accordingto the preliminary resection profile 150. The illustrated shims 400 maybe particularly useful if the preliminary resection profile is a curvedresection profile, although other shims, described below, may beparticularly useful if the preliminary resection profile is a planarresection profile. The shims 400 may be useful, for example, to providethe surgeon the ability to trial the femur using trial inserts notspecifically designed for use with the curved bone profile. In oneembodiment, as illustrated in FIGS. 8C-D, the shims 400 are designed inrelation to the femoral implant 180 and the curved resection profile.FIG. 8C illustrates the femoral implant 180, and FIG. 8D includes thecurved resection profile superimposed on the femoral implant 180. Theshims 400 each have an articulation surface configured to match theshape of the femoral implant 180, minus the curved resection profile. Afirst alternate pair of shims 400 a is illustrated in FIGS. 9A-B. Shims400 a are substantially identical to shims 400 with the exception thatshims 400 a include a peg 410 a on the bone contacting surface tofacilitate fixation to the distal femur 100. A second alternate pair ofshims 400 b is illustrated in FIG. 9C. Shims 400 b are substantiallyidentical to shims 400 a with the exception that each shim 400 bincludes a first peg 410 b near a first end and a second peg 410 b neara second end. As illustrated in FIG. 9D, the distal femur 100 may bemachined with corresponding holes to mate with first and second pegs 410b. A third alternate pair of shims 400 c is illustrated in FIG. 4E.Shims 400 c are substantially similar to shims 400 b, but do not includepegs 410 b and rather include a plurality of holes 420 c. Fasteners,such as bone screws, may be used to attach the shims 400 c to the distalfemur 100 through the holes 420 c.

It should further be noted that the interior of shims need not berounded. For example, as illustrated in FIG. 9F-G and as describedabove, the distal femur 100 may be prepared with a preliminary boneresection according to a preliminary resection profile 150 that consistsmostly of planar cuts. As can be seen, particularly in FIG. 9F, theplanar resection profile is offset a few millimeters from the finalprojected cut plan 170, much in the same way as described above inrelation to the curved resection profile. As illustrated in FIGS. 9H-J,shims 400 d with planar inner surfaces that correspond to the planarresection profile may be mated to the distal femur 100 in any of thepreviously described ways. Shims 400 d may be identical to any of thepreviously described shims, with the exception that the inner surfacesare planar and correspond to the planar resection profile illustrated inFIGS. 9F-G. Although the distal femur 100 cannot be used directly forintraoperative trialing in this case because of the preliminary boneresection according to the planar resection profile, shims 400 d providethe articulating surface which, along with the distal femur, correlatesto the distal-posterior condyles of the final femoral implant tofacilitate intraoperative trialing. This configuration may be especiallyuseful when the intended femoral implant is one without a “singleradius” configuration.

The distal femur 100 is illustrated in FIG. 10 after the preliminaryfemoral bone resection has been performed according to the curvedresection profile. However, shims 400 have been placed on the femoralcondyles 110, 115. The shims 400 provide an outer articulating surfacethat matches the shape of the femoral implant 180. In addition, thedesign of the shims 400 provides or maintains a flexion axis that iscoaxial with the flexion axis of the implant according to the finaldesign plan, such that trialing may be performed after the preliminaryfemoral bone resection has been completed.

One embodiment of a tibial trial insert 500 that may be used with thedistal femur 100 and shims 400 is illustrated in FIG. 11A. Tibial trialinsert 500 is a constant volume device that provides variable pressure,and may include load sensing capabilities to provide a variety ofmeasurements to the surgeon during trialing. A trial including loadsensing elements in the medial and lateral compartments may furtherinclude a receiver and/or a transmitter for receiving and/ortransmitting information regarding sensed load to a computer, which inturn may display the information on a display, such as a graphic userinterface (“GUI”), to inform the surgeon of loads being applied to theinsert trial. The information may be transmitted wirelessly or theinsert may be hardwired to a computer. Power may be supplied by the wireor otherwise, including, for example, battery power.

The shims 400 are not necessary for trialing in all cases, for exampleif trialing were performed with a trial insert designed specifically tobe congruent to a curved resection profile, such as tibial trial insert300 described with reference to FIG. 5. A constant volume trial mayprovide the surgeon with rectangular joint spaces/gaps during trialingassessment. With this space, the surgeon can assess the effect that thesurrounding soft tissue, including ligaments, tendons, etc., has on theoverall joint space and make necessary adjustments, such as performingligament releases.

Alternately, trialing may be performed using a constant pressure,variable volume trial insert 600 if desired. With a constant pressuretrial, as opposed to a constant volume trial, the joint may tend to finda position of equilibrium that results in a malposition or imbalance(i.e. varus or valgus) during trial assessment. In this mode, thesurgeon addresses the variable volume by, for example, performingligament releases iteratively until the malposition or imbalance iscorrected. For example, FIG. 11B illustrates a tibial trial insert 600that includes an insert surface 610, which may be similar or identicalto the tibial trial insert 500. The insert surface 610 is connected to acomponent with a volume that may expand or contract, for example bellows620. Bellows 620 may be connected to a fluid source through the lumen ofa tube 630. The fluid source may, for example, be capable of pumping airor saline into the bellows 620 through the tube 630 to provide forconstant pressure and variable volume during trialing. The insertsurface 610 may also be modified to have the surface 610′, illustratedin FIG. 11C. Insert surface 610′ is substantially the same as thesurface of tibial trial insert 300 described above with reference toFIG. 5. Essentially, insert surface 610′ includes a sulcus or groove620′, 630′ for each femoral condyle 110, 115 to provide for articulationwith the distal femur 100 without the need for shims 400. Anotherembodiment of a variable volume insert 600 a is illustrated in FIG. 11D.This insert 600 a is similar to insert 600, but includes two separatesurfaces 610 a and bellows 620 a, each attached to a tube 630 a. Thisembodiment provides for independent filling of the portions of insert600 a corresponding to the separate medial and lateral femoral condyles110, 115. As illustrated in FIG. 11E, a solid member 640 a may be usedto physically (but not fluidly) connect the separate bellows 620 a forease of handling, insertion, etc.

A number of variations may be made to the tibial trial inserts for usewith the native bone (with or without shims 400) of the distal femur 100after the preliminary bone resection has been performed according to thepreliminary resection profile 150. For example, a modular tibial trial700 is illustrated in FIGS. 12A-B. The modular tibial trial 700 mayinclude an insert 710 and a shim 720. The insert 710 may have a numberof features similar to other inserts described herein. For example, theinsert 710 may include a first condylar portion 711 and a secondcondylar portion 712 connected by a bridge 713 at anterior ends of thefirst and second condylar portions. A proximal surface of the firstcondylar portion 711 may include a sulcus or groove 714 and a proximalsurface of the second condylar portion 712 may also include a sulcus orgroove 715. As described above, each groove 714, 715 may be configuredto correspond with the dished plateaus of the tibial implant and providearticulation with the machined surface of the distal femur 100 after itis resected according to the preliminary resection profile 150. Thedistal surface of the insert 710 may include pegs 716, 717 configured tobe inserted in corresponding holes in the shim 720 (holes not visible inFIGS. 12A-B).

Another embodiment of a tibial trial 800 is illustrated in FIGS. 13A-B.Similar to trial 700, trial 800 is modular and may be used with thenative bone of the distal femur 100 (with or without shims 400) afterthe preliminary resection has been performed according to thepreliminary resection profile 150. Tibial trial 800 may include aninsert 810 and a template 820. The insert 810 may have a number offeatures similar to other inserts described herein. For example, insert810 may include a first condylar portion 811 and a second condylarportion 812. A proximal surface of the first condylar portion 811 mayinclude a sulcus or groove 814 and a proximal surface of the secondcondylar portion 812 may also include a sulcus or groove 815. Althoughthe grooves 814, 815 are described as being included on the proximalsurfaces of the first and second condylar portions 811, 812, it shouldbe apparent that the grooves may take the form of a continuous grooveacross the proximal surface of the insert 810. As described above, eachgroove 814, 815 may be configured to correspond with the dished plateausof the tibial implant and provide articulation with the machined surfaceof the distal femur 100 after it is resected according to thepreliminary resection profile 150. The distal surface of the insert 810may be configured be inserted into the template 820 by, for example,press-fitting, snap fitting, tongue-in-groove fitting, etc.

The template 820 may include a plurality of fixation holes 822 at ananterior end of the template. The template 820 may be fixed to theproximal tibia 200 with fixation pins that extend through fixation holes822 and into the bone. The fixation holes 822 may be angled, allowing asurgeon to insert fixation pins through the fixation holes 822 with lessclearance required than if the fixation holes were not angled. Requiringless clearance may be beneficial, for example, because it may allow asurgeon to fix the template 820 to the bone without repositioning, oronly minimally repositioning, the distal femur 100, proximal tibia 200,or other portions of the patient's anatomy.

A further embodiment of a tibial trial 900 a is illustrated in FIGS.14A-B. Similar to trial 800, trial 900 a is modular and may be used withthe native bone of the distal femur 100 (with or without shims 400)after the preliminary resection has been performed according to thepreliminary resection profile 150. Tibial trial 900 a may include aninsert 910 and a template 920 a. The insert 910 may have a number offeatures similar to other inserts described herein. For example, insert910 may include a first condylar portion 911 and a second condylarportion 912. A proximal surface of the first condylar portion 911 mayinclude a sulcus or groove 914 and a proximal surface of the secondcondylar portion 912 may also include a sulcus or groove 915. Althoughthe grooves 914, 915 are described as being included on the proximalsurfaces of the first and second condylar portions 911, 912, it shouldbe apparent that the grooves may take the form of a continuous grooveacross the proximal surface of the insert 910. As described above, eachgroove 914, 915 may be configured to correspond with the dished plateausof the tibial implant and provide articulation with the machined surfaceof the distal femur 100 after it is resected according to thepreliminary resection profile 150. The distal surface of the insert 910a may include pegs 916, 917 configured to be inserted in correspondingholes in the template 920 a (holes not visible in FIGS. 14A-B).

The template 920 a may include a plurality of fixation holes 922 a at ananterior end of the template. The template 920 a may be fixed to theproximal tibia 200 with fixation pins that extend through fixation holes922 a and into the bone. The fixation holes 922 a may be angled,allowing a surgeon to insert fixation pins through the fixation holes922 a with less clearance required than if the fixation holes were notangled. The template 920 a may also include a groove 930 a on ananterior portion thereof. The groove 930 a may provide clearance betweenthe template 930 a and the insert 910 such that a surgeon may relativelyeasily grasp and remove insert 910 from template 920 a if desired.

The insert 910 and template 920 a may be part of a set or a kit ofinserts and templates. For example, one exemplary kit may include asmall insert 910 and four increasingly sized templates 920 a-d, withtemplate 920 a being the smallest and 920 d being the largest, asillustrated in FIGS. 14C-F. The kit may also include a large insert andanother four sized templates (not illustrated). Even further, each ofthe small and large inserts may be provided with a number of differentthicknesses. In one embodiment, the kit contains five thicknesses foreach of the small land large inserts, for a total of ten inserts andeight templates. As with other modulate trials described herein, thetemplates 920 a-d may each be able to mate with inserts other thaninsert 910 to allow a surgeon the flexibility to use a traditionalinsert with one of the templates 920 a-d in conjunction with the distalfemur 100 with shims 400 attached.

Another monolithic trial insert 1000 a is illustrated in FIG. 15A. Thetrial insert 1000 a may be a single piece. The insert 1000 a may have anumber of features similar to other inserts described herein. Forexample, the insert 1000 a may include a first condylar portion 1010 aand a second condylar portion 1020 a connected by a bridge 1030 a atanterior ends of the first and second condylar portions. A proximalsurface of the first condylar portion 1010 a may include a sulcus orgroove 1040 a and a proximal surface of the second condylar portion 1020a may also include a sulcus or groove 1050 a. As described above, eachgroove 1040 a, 1050 a may be configured to correspond with the dishedplateaus of the tibial implant and provide articulation with themachined surface of the distal femur 100 after it is resected accordingto the preliminary resection profile 150. Trial insert 1000 a may bepart of a set or a kit of different sized monolithic trial inserts. Inone example, a kit of trial inserts may include two groups of fourinserts for a total of eight inserts. The four inserts of a first groupmay each have an identical or nearly identical profile, as illustratedin FIG. 15B, but each have different perimeters. Similarly, the fourinserts of a second group may each have an identical or nearly identicalprofile, the profile of the inserts of the second group being greaterthan the profile of the inserts of the first group. Again, each insertin the second group may have a different perimeter with respect to oneanother. FIG. 15C particularly illustrates the difference in perimetersizes of two inserts 1000 a, 1000 b of an exemplary kit.

It may also be desirable to have a single tibial trial 1100 that can beused with a distal femur 100 (with or without shims) resected accordingto a preliminary resection profile 150 and also with after the finalcuts have been performed. FIGS. 16A-B illustrate such a tibial trial1100. Tibial trial 1100 includes a first insert 1110 and a second insert1120. First insert 1110 takes a similar form to certain embodimentsdescribed above. For example, first insert 1110 may include a firstcondylar portion 1111 and a second condylar portion 1112 connected by abridge 1113 at anterior ends of the first and second condylar portions.A proximal surface of the first condylar portion 1111 may include asulcus or groove 1114 and a proximal surface of the second condylarportion 1112 may also include a sulcus or groove 1115. As describedabove, each groove 1114, 1115 may be configured to correspond with thedished plateaus of the tibial implant and provide articulation with themachined surface of the distal femur 100 after it is resected accordingto the curved resection profile. The distal surface of the first insert1110 may include pegs 1116, 1116 configured to be inserted incorresponding holes in 1126, 1127 in the second insert 1120.

The second insert 1120 may also have a first condylar portion 1121 and asecond condylar portion 1122 connected by a bridge 1123 at anterior endsof the first and second condylar portions. The proximal surface of thesecond insert 1120 may take a traditional shape capable of articulatingwith the distal femur 100 after a final cut has been made followingintraoperative trialing with the first insert 1100. Tibial trial 1100allows a surgeon to dynamically trial the distal femur 100 that has beenresected according to the preliminary resection profile 150. The surgeonmay then, when satisfied, perform the final cuts. After performing thefinal cuts, the surgeon may remove the first insert 1110 from firsttrial 1100, leaving the more traditional surface of second trial 1120available for standard trialing.

Another insert 1200 capable of dual use is illustrated in FIGS. 17A-B.Insert 1200 may include a first condylar portion 1211 and a secondcondylar portion 1212 connected by a bridge 1213 at anterior ends of thefirst and second condylar portions. The proximal surface of the firstand second condylar portions 1211, 1212 are configured to articulatewith the distal femur 100 according to standard trialing methods after afinal cut has been performed on the femur. However, first condylarportion 1211 includes two holes 1216 and second condylar portion 1212includes two holes 1217. Holes 1216, 1217 are configured to accept pegs1227 of a sulcus insert or groove insert 1220 (only one groove insertillustrated in FIG. 17A). Each groove insert 1220 includes a sulcus orgroove 1224 on an articulation surface thereof. When used without grooveinserts 1220, insert 1200 may perform as more traditional trial insertsdo. However, if the surgeon prefers to dynamically trial the distalfemur 100 after performing a preliminary resection according to thepreliminary resection profile 150, a groove insert 1220 may be attachedto each of the first and second condylar portions 1211, 1212 of theinsert 1200, providing a surface that may articulate directly with themachined surface of the distal femur. As should be appreciated, insert1200 provides a surgeon the ability to dynamically trial the femur 100following a preliminary resection when the groove inserts 1220 areattached, and then perform final cuts to the femur and then performstandard trialing after removing the groove inserts 1220 from the trialinsert 1200.

In an exemplary knee replacement procedure, such as a cruciate retaining(“CR”) TKA, the surgeon may begin by creating an incision at thesurgical site and mounting anatomy trackers, such as femoral or tibialtrackers. The bones are registered to allow a guidance system to trackthe position of the bones during the procedure. A navigation system witha GUI and other components known in the art may be used to verify theregistration and the planned implant position. At this point, thesurgeon may perform an initial kinematic analysis of the knee including,for example, analysis of the pre-operative implant positions, checkingthe implant design plan against actual bone overlap, and checkingflexion and extension gaps. The surgeon may, if satisfied, verify theoperative plan and begin the procedure. Following this initial kinematicanalysis, if performed, the surgeon may position the machining robot andapply retractors to the incision in preparation of machining the bone.

The robot may perform the preliminary bone resection of the distal femur100 and proximal tibia 200 using, for example, a large barrel bur, suchas a 6, 8 or 10 mm bur. However, other machining tools and other sizeburs may be used, and the examples provided are meant only to beillustrative. The same bur may also be used to perform the preliminarymachining of both the distal femur 100 and the proximal tibia 200, ifdesired. The distal femur 100 and proximal tibia 200 may also bemachined simultaneously. As described above in relation to FIGS. 1-4D, apreliminary bone resection may be performed on the distal femuraccording to the preliminary resection profile 150, such as the curvedresection profile, while a preliminary bone resection may be performedon the proximal tibia according to a separate preliminary resectionprofile 250. Having been described previously, the particular details ofthe preliminary resection profiles 150, 250 are not repeated here.

After the preliminary bone resection is complete for both the distalfemur 100 and the proximal tibia 200, intraoperative trialing, includingkinematic analysis and gap balancing, may be performed. To perform theintraoperative trailing and gap analysis, the surgeon chooses a desiredtrial component. The particular trial component may be a componentdescribed herein or any other suitable component. If trialing themachined distal femur 100 according to the curved resection profilecorresponding to a “single radius” femoral implant 180, a trial insertdesigned for use with the native resected femur, such as one with asulcus or groove for each condyle, is preferred. However, as describedabove, other preliminary resection profiles, including a planarresection profile, may be implemented for other types of femoralimplants, in which a flexion axis is derived from the particular implantand a preliminary femoral resection is made. The geometry of thepreliminary femoral bone resection with other apparatus, such as shims400, corresponds to the geometry of the femoral implant such thatintraoperative trailing is indicative of the kinematics of the implantsystem according to the final design plan. In these cases, it may bedesirable to perform the intraoperative trialing with a more traditionalcomponent, including certain embodiments described herein. The surgeonmay perform a second kinematic analysis including gap balancing at arange of angles of flexion and extension, as described above withreference to FIGS. 7A-B. If the values determined from kinematicanalysis meet the surgeon's targets, he may continue to the next step.If the values do not meet the surgeon's targets, he may take correctiveaction, such as releasing soft tissue, changing the planned position ofthe implant, or performing a second machining step to further resect thebone. These steps may be performed in an iterative fashion, fine tuningthe bone, tissue, and final implant position for an optimal result. Thismay be possible, in part, to the remaining bone stock, at approximately2 mm to approximately 3 mm, as the surgeon may still reshape theremaining bone stock as desired. Preferably, the surgeon will be able toperform this fine tuning up with a variation up to between approximately2 mm and approximately 3 mm (translational) and up to approximately 2degrees (angular) from the original final design plan.

After the surgeon is satisfied with the second kinematic analysis, anyintraoperative gap balancing performed, and any revisions to thepreoperative plan, the distal femur 100 and proximal tibia 200 may befinished. The robot may finish the distal femur 100 according to thefinal projected femoral cut plan 170, or a modified plan if the femoralcut plan 170 was modified by the surgeon as a result of the secondkinematic analysis and/or intraoperative gap balancing. Similarly, therobot may finish the proximal tibia 200 according to the final projectedtibial cut plan 270, or a modified plan if the projected tibial cut plan270 has been modified by the surgeon.

After the finishing cuts are made to the distal femur 100 and proximaltibia 200, the surgeon may perform traditional trial reduction andanalysis, as is known in the art, along with a third kinematic analysis.If a dual use trial insert was used for the dynamic trialing, such asthose described in relation to FIGS. 16A-B and 17A-B, the surgeon maysimply modify the insert as described so that it may be used again inits modified form for this stage of trialing. At this stage, the surgeonmay make any final adjustments deemed necessary and implant the femoralimplant 180 onto the distal femur 100 and the tibial implant 280 ontothe proximal tibia 200. The surgeon may perform a fourth and finalkinematic analysis to assess the final positions of the implants 180,280.

It should be noted that, although trialing and kinematic analysis hasgenerally been discussed in relation to the tibia and femur, the dynamictrialing may also assist in optimizing patellar tracking, placemen, andextensor mechanism tightness. This is because, at least in part, dynamictrialing may involve the kinematics of the entire joint, of which thepatella is a part.

As should be appreciated, performing a knee replacement according to theabove description provides the surgeon the ability to fine tune thepreoperative plan while simultaneously reducing complexity, cost, andoperation time compared to previously known methods and apparatus.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims. For example,the principles described herein may be applicable to other jointprocedures including, for example, hip arthroplasty.

It will be appreciated that the various dependent claims and thefeatures set forth therein can be combined in different ways thanpresented in the initial claims. It will also be appreciated that thefeatures described in connection with individual embodiments may beshared with others of the described embodiments.

1. A dynamic trialing method comprising: creating a bone model of adistal femur of a patient; determining a preliminary curved resectionprofile on the bone model offset from distal and posterior nonresectedarticular surfaces of the distal femur; resecting the distal femur bymaking a preliminary resection along the preliminary curved resectionprofile such that a first area of bone is removed from the distal femur;engaging the resected distal femur to a tibial trial coupled to aresected proximal tibia; and performing intraoperative kinematicanalysis by at least articulating the proximal tibia with respect to thedistal femur.
 2. The dynamic trialing method of claim 1, wherein thestep of performing kinematic analysis further includes performingintraoperative gap balancing.
 3. The dynamic trialing method of claim 2,further comprising: making a subsequent resection of the distal femursuch that a second area of bone is removed from the distal femur.
 4. Thedynamic trialing method of claim 3, wherein the subsequent resectionincludes making planar bone resections corresponding to mating surfaceson a femoral implant.
 5. The dynamic trialing method of claim 4, whereinthe subsequent resection is performed according to a final design plan.6. The dynamic trialing method of claim 4, wherein the subsequentresection is performed according to a modified final design plan, themodified final design plan being determined, at least in part, basedupon results of the kinematic analysis.
 7. The dynamic trialing methodof claim 1, wherein the tibial trial includes a first condylar portionconnected to a second condylar portion, the first and second condylarportions each having a groove corresponding to an articular dish of atibial implant plateau.
 8. The dynamic trialing method of claim 7,wherein the tibial trial includes a tibial trial insert and a template,the tibial trial insert being removable from the template.
 9. Thedynamic trialing method of claim 8, further comprising the step ofremoving the tibial trial insert from the template and inserting analternative modular tibial trial insert into the template.
 10. Thedynamic trialing method of claim 7, wherein the tibial trial includes afirst insert having a proximal surface and a distal surface and a secondinsert having a proximal surface, the proximal surface of the firstinsert having two grooves corresponding to articular dishes of thetibial implant plateau.
 11. The dynamic trialing method of claim 10,wherein the first insert has at least two pegs extending distally fromthe distal surface of the first insert and the second insert has atleast two holes on the proximal surface of the second insert, the atleast two pegs being configured to be inserted into the at least twoholes.
 12. The dynamic trialing method of claim 7, wherein the tibialtrial includes a tibial insert having a first condylar portionconfigured to mate with a first groove insert and a second condylarportion configured to mate with a second groove insert, the first andsecond groove inserts each having an articulation surface correspondingto the articular dish of the tibial implant plateau.
 13. The dynamictrialing method of claim 1, further comprising the step of couplingfirst and second femoral shims to first and second condyles of thedistal femur after the step of resecting the distal femur by making apreliminary resection.
 14. The dynamic trialing method of claim 13,wherein the first and second femoral shims each have an articulationsurface corresponding to a shape of the femoral implant.
 15. The dynamictrialing method of claim 14, wherein the first and second femoral shimseach have a bone contacting surface with a peg extending therefrom, thepegs being configured to facilitate fixing the first and second femoralshims to the resected distal femur.
 16. The dynamic trialing method ofclaim 1, wherein the tibial trial includes a first condylar portion, asecond condylar portion, and at least one insert surface, the at leastone insert surface being connected to at least one expandable componenthaving a volume that may expand or contract and also being configured toremain at a constant pressure.
 17. The dynamic trialing method of claim16, wherein the tibial trial has exactly one insert surface and exactlyone expandable component, the first and second condylar portions beingconnected to one another.
 18. The dynamic trialing method of claim 16,wherein the tibial trial has two insert surfaces and two expandablecomponents, a first insert surface corresponding to a first expandablecomponent and the first condylar portion, and a second insert surfacecorresponding to a second expandable component and a second condylarportion.
 19. The dynamic trialing method of claim 18, wherein the tibialtrial includes a connecting member physically connecting the firstcondylar portion to the second condylar portion, the first expandableportion being fluidly isolated from the second expandable portion. 20.The dynamic trialing method of claim 16, wherein the at least oneexpandable component is a bellows.
 21. The dynamic trialing method ofclaim 20, wherein the at least one expandable component is connected toa fluid source.
 22. The dynamic trialing method of claim 21, wherein thefluid source is configured to pump air into the at least one expandablecomponent.
 23. The dynamic trialing method of claim 21, wherein thefluid source is configured to pump saline into the at least oneexpandable component.
 24. A dynamic trialing method comprising: creatinga bone model of a distal femur of a patient; determining a preliminaryresection profile on the bone model; and resecting the distal femur bymaking a preliminary resection along the preliminary resection profilesuch that a first area of bone is removed from the distal femur, whereinthe preliminary resection profile is determined, at least in part, basedon a feature of a final design plan of a femoral implant.
 25. Thedynamic trialing method of claim 24, wherein the final design plan ofthe femoral implant includes a femoral implant flexion axis, and thepreliminary resection profile is based on the femoral implant flexionaxis.
 26. The dynamic trialing method of claim 25, wherein thepreliminary resection profile includes a flexion axis, the flexion axisof the preliminary resection profile being coaxial with the femoralimplant flexion axis.
 27. The dynamic trialing method of claim 24,further comprising the step of performing intraoperative kinematicanalysis by at least articulating the proximal tibia with respect to thedistal femur.
 28. The dynamic trialing method of claim 27, furthercomprising the step of performing intraoperative gap balancing.